This invention relates to an ignition system for an internal combustion engine.
In one type of ignition system for an internal combustion engine known in the art as a CDI system, a magnet is mounted to a rotary member, such as a flywheel, which rotates in synchronism with a rotary shaft of the internal combustion engine and acts on a generating coil to cause same to generate an electromotive force while the flywheel is rotating, the generating coil passing a current to an ignition capacitor to charge same. A trigger voltage for causing a thyristor of an ignition circuit to fire is produced at a predetermined time to cause the ignition capacitor to discharge and cause an ignition coil to generate a high voltage, so that a spark discharge will take place in an ignition plug of the internal combustion engine. The time at which ignition is effected is predetermined at all times regardless of the revolution speed of the internal combustion engine.
Generally, it is desirable, to enable the internal combustion engine to exhibit high performance, that the time at which ignition takes place be delayed in a range of low engine speeds when the engine is started or the engine idles, that the time at which ignition takes place be advanced in a range of high engine speeds, and that the time at which ignition takes place be gradually advanced as the engine speed increases in a range of medium engine speeds. However, in the type of ignition system described hereinabove, the time at which ignition takes place is predetermined irrespective of the revolution speed of the internal combustion engine and the time at which ignition takes place is altered in a monent when a predetermined revolution speed is exceeded. Thus, it has hitherto been impossible for the ignition system of the prior art to meet the aforesaid requirements.